I've been all around the mirrorless world for a while (extensive experience using Micro 43, Fuji X and the original A7r). I had a serious look at the A7rII, and ended up getting out of Sony and putting a big deposit on an X-Pro 2 instead - here's why (for my specific needs).
1.) How big do you need to print? I own an Epson 7900, but don't have easy access to a 9900 anywhere, so my printing tends to go right up to 24x36, but stop there. My X-T1 is an "almost" at 24x36 - it works for many scenes, but there are some where it's not quite there. A much newer sensor with 1.5x the pixels should take the "almost" off of that. Micro 43 has never gotten there - it's ideal at 12x18, "almost" at 16x24. The A7r (original) is 24x36 easy, with some room to grow, and the A7rII is probably somewhat better.
2.) Weather sealing - the Sonys claim it, but I've never trusted it (it seems to be based on tolerances, not actual o-ring seals). Both Fuji and Olympus publish diagrams of their sealing, and the sealed Fujis are at least D800 class, while the best Olympi are in the D4/1Dx class.
3.) Lenses. FE lenses are huge and there's a limited selection, Fuji has a GREAT range of relatively compact lenses, Micro 43 has more variability in quality, but some great glass.
If I were doing less of my photography in the backcountry, and more close to the car, my considerations for an ultimate image quality system would be different from "the best image quality I'm willing to carry". I'd look at Sony with a mix of native and adapted lenses, Nikon (D810), and the Pentax 645Z. Canon's limited DR wouldn't be as appealing, and Phase and Hasselblad would be out of my price range. Sony might VERY WELL win that competition!
I might do down this path myself.
I'm personally all over the map. I'm an MFA grad student and before entering school I was pure analog, mainly 8x10 with 4x5 sprinkled in. Personally, I'll never get rid of these formats. School turned me to digital, due to turn around times and print expectations for weekly crits. At this point I've shot everything, A7RII, D810, 645Z, and now a CFV-50C , which is likely going up for sale. Of all the cameras I loved the Z the most but it actually failed me, a mirror mechanism failure 21 days into owning it.
We have three Epson 9900's and a 7700 for the grads. I'm starting to question how big I'll print in the long run. With these massive MFDB files I can't print huge, 40x60 but am I really going to print this large once I'm done with school? Likely not.
I'm in the A7RII felt like a toy camp.
I have some cash now and need to decide between repurchasing the Sony or going XPro2, which would ultimately save me coin in the long run.
I just need to think, can the Xpro2 absolutely get me a 24x20 print. I've seen a fellow classmate make an absolute f'n killer 40x60 from an A7RII... We were looking at it right at the paper level and it held up so damn well, printed at like 190DPI.
Sent from my iPhone using Tapatalk